Why Your Urine Turns Highlighter Yellow After Vitamin C Drinks (Most People Get This Wrong)! If you've ever taken Redoxon, Berocca, or any soluble Vitamin C drinkand suddenly your urine looks like Why Is My Pee Neon Yellow? Doctor Explains Why This Happens Vitamin B supplements, especially those containing riboflavin (vitamin B2), often cause bright yellow or neon colored urine. This happens because excess riboflavin is water soluble and is excreted through urine when the body has The 7 Colors of Urine and Their Associated Health Indicators Bright yellow urine: Colors, changes, and causes Glutathione Antioxidant that supports detoxification, immune health, and brighter skin.